What is the limit for free reading? I've heard this a few times now from a few different sources, but I've never run into it myself.
Three or four articles a day, I can't remember.
Not very high if you browse, but adequate if you get a link or two from other sources.
I wish they adopted the bandcamp model: quite a number of tracks for free per day, but you can instantly pay for the one you liked, the amount you like (above a certain minimum). This way, the articles I personally find valuable would be both easier for me to find, and paid by me higher than the slice of the common subscription funds they receive now.
I stopped doing both, though: you can't read too much for free, but more than half of the content was not worth reading (for me), except maybe for quick skimming. There definitely are articles on Medium that are gems (again, from my POV), but I hope them to be brought to me by social networks anyway.
For authors, though, Medium must be pretty valuable, bringing relevant readers, and maybe some ad revenue. It does have a discovery feature which may be not brilliantly great, but is still quite OK, especially if you have time to spend on lighter reading.